Remove the "total account slots = sum of each character slot /1, /2, /3, /4, /5 etc." mechanic altogether.
PS: Didn't really want to make a vote-able suggestion, since I believe certain colo-whores (myself not included) and similar P2W mechanically minded players with large swaths of accounts would have the ability to tremendously down-vote this =/. However, since it was requested, here it is anyways! =)
Rhys